1. Field of the Invention
This invention relates to a liquid injection recording apparatus and a capping device suitably used in the apparatus.
2. Description of the Prior Art
The liquid injection recording apparatus is called an ink jet printer and is an apparatus in which recording liquid (ink) is discharged from orifices communicating with a liquid flow path filled with the liquid to form flying liquid droplets and dot recording is effected on a recording medium by the liquid droplets.
In such a recording apparatus, there is generally provided a capping device for preventing drying of the ink in and near the orifice portion and for recovering the discharge function of the apparatus when it occurs that an ink-discharge operation of the apparatus can not be performed.
Such a capping device is usually provided at the home position of a carriage having a recording head mounted thereon and effects the capping operation including the operation for recovering the discharge function. It is known, during the non-discharge recovering operation, to reduce the pressure in a sub-tank provided on the recording head side by a negative pressure sucking operation through a cap, whereby the liquid is sucked from the orifices to recover the discharge function by which liquid droplets are discharged from the orifices.
However, if the cap is removed before the reduced pressure in the sub-tank recovers the normal pressure level, air may sometimes be sucked from the orifices.
As a result, there have occurred cases where the meniscus which is the fore end portion of the liquid in the nozzle retracts or bubbles are brought over into the liquid flow path, so that in spite of the operation for recovering the discharge function having been effected, the liquid still can not be discharged.
For this reason, it has been necessary to delay the cap release until the pressure in the sub-tank resumes its original level.
Thus, heretofore, a contrivance has been made such that the time until the pressure in the sub-tank regains its original level is electrically counted and the operator is informed of the time till the cap release by flicker of a lamp or the like, thereby letting the operator know the point of time at which the cap release can be effected.
However, even if such a structure is adopted, it has sometimes been the case that some users who do not understand the meaning of the flicker of the lamp or the like prematurely effect the cap release to cause the problem described above to occur.
Thus, a structure for locking the capping device until the pressure in the sub-tank regains its original level has been proposed.
A conventional device of such a structure is shown in FIGS. 1 to 4 of the accompanying drawings.
In FIG. 1, reference numerals 1 and 2 designate cartridges each having a bag member 3 containing liquid such as ink therein and removably mountable with respect to a recording apparatus.
In the following description, the bag members 3 for storing ink therein will be referred to as the main tanks.
A chamber partitioned from the main tank 3 is formed in the lower portion of the cartridge 1, and a waste liquid absorbing member 4 formed of sponge or the like is contained in this chamber so as to provide a waste liquid reservoir.
Reference numeral 5 designates a recording head for injecting liquid and effecting the recording. The recording head 5 is mounted on a carriage, not shown.
The rear half of the recording head provides a sub-tank 7 which is connected to the main tanks 3 by supply tubes 6 so that liquid 8 is supplied from the main tanks 3 into the sub-tank 7 through the supply tubes 6.
A supply pipe 9 is immersed in the liquid 8 within the sub-tank 7, and nozzles provided with orifices for discharging the liquid are connected to the supply pipe 9.
Although not shown, energy generating members such as electro-mechanical converting members comprising piezo elements or electro-thermal converting members such as heat-generating resistance members are provided near the fore ends of these nozzles, and by applying to these energy generating members an input signal conforming to a printing command, the energy for liquid droplet discharge is imparted to the liquid in the nozzles, whereby the liquid in the nozzles is discharged as liquid droplets from the unshown orifices of the recording head, and thus, dot printing is effected on a recording medium, not shown.
In FIG. 1, the device is shown in a state in which capping means has been operated.
Designated by 10 is a pump having a piston 11 therein. A push button 12 integral with the piston 11 extends upwardly through the upper end of the cylinder of the pump.
A cap 14 is connected to the pump 10 through nozzle tubes 13.
The cap 14 bears against the fore end portion of the recording head 5 and prevents clogging of the orifices, etc., resulting from the drying of the liquid in and near the orifice portions when not used and sucks the liquid from the orifices to thereby effect the recovering operation to ensure that the liquid droplets can be discharged.
One end of each suction tube 15 is connected to the pump 10 and the other end of each suction tube 15 is connected to the sub-tank 7, and the position at which the other end of each suction tube 15 is connected to the sub-tank 7 is higher than the position at which the supply tubes 6 are connected to the sub-tank 7.
One end of a waste liquid tube 16 is connected to the lower end of the pump 10 and the other end thereof is connected to the aforementioned waste liquid reservoir.
The piston 11 is normally biased upwardly by a spring, not shown.
A driving mechanism for the pump 10 is constructed as shown in FIG. 2.
That is, the pump 10 is fixed to a base 17 and the cap 14 is slidably fitted in a cap device 18.
One end of a lever 20 is pivotally supported on the base 17 through a support plate 19 and a projecting piece of flange 21 is provided on the fore end of this lever 20.
A guide slot 21a (shown as being of an inverted dog-legged shape) is formed in the projecting piece 21, and a pin 22 projecting from a cap holder 14a constituting the cap 14 as shown in FIG. 4 is slidably fitted in the guide slot 21a.
The pin 22 projects outwardly through a horizontal slot 18b formed in a side surface of the casing 18a of the cap device 18.
The cap holder 14a is provided with a rubber cap 14b, which is urged against the front face of the recording head.
The cap holder 14a is normally biased in a direction to jut out by a spring 23 as shown in FIG. 4.
A spring 24 is extended beyond a shaft 20a pivotally supporting the lever 20 and between the vicinity of the guide slot 21a and the fixed portion of the device, and biases the lever 20 clockwise as viewed in FIG. 3.
A projection 20b is provided on the underside of the lever 20, and is opposed to the push button 12 of the pump 10.
A projecting piece 20c is also provided on the underside of the lever 20 so as to be able to contact a switch SW1 fixed to the base 17.
On the other hand, as shown in FIG. 2, a solenoid 25 is fixed on the base 17 and the lower end of a lock lever 26 is pivotally connected to the fore end of the rod 25a of the solenoid 25.
The intermediate portion of the lock lever 26 is pivotally supported by a shaft 27, on which a torsion coil spring 28 is wound.
Accordingly, unless the solenoid 25 is electrically energized to attract the rod 25a, the lock lever 26 is at a position retracted from the free end of the lock lever 20, and one can freely operate the pump 10.
Under the above-described structure, the operations for capping and recovering the discharge function are effected in the following manner.
Where the liquid injection recording apparatus is not used for a long time, and during the transportation of the apparatus, the cap 14 bears against the recording head to prevent the liquid such as ink in the nozzle portion from drying or leaking.
At such time, the lever 20 is pivoted clockwise as viewed in FIG. 2 and the lock lever 26 assumes its upright position and locks the lever 20 as that the lever 20 cannot be raised.
Also, at this time, as shown in FIG. 3A, the lever 20 is pivoted clockwise by the force of the spring 24 and the pin 22 lies at the upper end of the guide slot 21a, and the cap 14 is retracted into the casing 18.
When, in this state, the free end of the lever 20 is pushed, the projection 20b of the lever 20 begins to depress the push button 12 of the pump 10 as shown in FIG. 3B.
At the same time, the pin 22 is guided to the intermediate portion of the guide slot 21a and advances into the slot 18b, and the cap 14 juts out, whereby the recording head is capped.
When the lever 20 is further depressed, the push button 12 of the pump 10 is further depressed and the piston 11 is lowered.
The piston 10 first closes its nozzle tube 13 side in the course of its lowering operation and air is sucked from the sub-tank 7 side through the suction tubes 15.
As a result, the pressure in the sub-tank 7 is reduced and the liquid is supplied from the main tanks 3 into the sub-tank 7 through the supply tubes 6.
When the liquid enters the sub-tank 7 and the suction tubes 15 by the pumping operation, the impedance on the suction tube 15 side becomes higher, and thereafter, the piston 11 no longer closes its nozzle tube 13 side and therefore, the liquid begins to be sucked from the nozzle side through the cap 14.
As a result, the bubbles or the like in the nozzles are removed and the recovery of liquid discharge function is effected.
Now, during this sucking operation, the switch SW1 is closed as shown in FIG. 3C.
On the other hand, when the operation for recovering the discharge function is being effected with the lever 20 pushed by the utilization of the lock lever 26, the hook 26a at the upper end of the lock lever 26 is brought into engagement with a projection 29 provided on the lever 20 to thereby keep the lever 20 in its depressed position, and after the pressure in the sub-tank has been restored to its original level, the solenoid 25 is operated to release the engagement.
That is, heretofore, the lever has been locked until the pressure in the sub-tank regains its original level, and after the pressure in the sub-tank has done so, the capping has been automatically released by the solenoid 25.
However, the locking by the lock lever 26 is of a simple structure provided by the engagement between the hook 26a and the projection 29, and this has sometimes given rise to the problem that when shocks or vibration is imparted to the hook 26a, the hook is simply disengaged from the projection 29 and the capping is released.
The occurrence of that problem in turn has sometimes led to the occurrence of another problem, that the function of preventing outflow of the liquid from the nozzles during transportation, which is another function of the capping device, and the function of preventing the clogging of the orifices of the nozzle due to the drying of the liquid therein when the apparatus is not used for a long time cannot be performed at all.